U.S. Pat. Nos. 4,397,164 and 4,329,750 of common assignee disclose a yarn finish applicator in which finish is metered to a slot running from top to bottom of the applicator. The yarn finish applicator of U.S. Pat. Nos. 4,397,164 and 4,329,750 includes a body member that has top, opposed side, front and back surfaces. A slot with bottom and side walls is formed in the front surface running from top to bottom of the body member. The slot has bottom and side walls with a passage connecting the back surface of the body member through which is metered the desired quantity of liquid finish. The lower portion of the front and back surfaces of the body member are angled downwardly toward each other and in conjunction with the opposed side surfaces which taper downwardly toward each other form an edge at the bottom wall of the slot. Liquid finish is applied to the yarn through a passage in the bottom wall of the slot and the applicator is capable of uniformly applying a finish to the yarn.
Pending application Ser. No. 07/148,584, also of common assignee, discloses a yarn finish applicator having a passage connecting the back surface of the body member to the slot by extending through the bottom wall of the slot and through a portion of each side wall adjacent the bottom wall. This applicator provides enhanced uniformity of finish application when, on occasion, threadline misalignment occurs with respect to the slot in the applicator.
If the above-described finish applicators are to be used for applying a finish which requires heating for application to the yarn, finish is typically supplied to the applicator from a remote reservoir of heated finish. However, for viscous finishes, the uniformity of finish applied is not as high as is desirable due to the inability to accurately control the temperature of and thus the viscosity of the finish being supplied to the yarn in the slot. Moreover, the difficulty increases as the number of finish application positions in a spinning machine increases. Control of finish temperature is particularly a problem during start-up when supply lines are cold and the heated finish is cooled before it reaches the slot. While the finish may be "overheated" at the reservoir so that it reaches the applicator at a desired temperature, this poses the risk that the finish may be degraded.